Technical Field
[0001] The present invention relates to a fuel injection valve used in an accumulator-type
fuel injection control device of an internal combustion engine.
Background Art
[0002] Conventionally, there has been known a fuel injection valve which is used in an accumulator-type
fuel injection control device of an internal combustion engine, where the fuel injection
valve injects high pressure fuel supplied from a common rail (accumulator) into cylinders
of the internal combustion engine. The fuel injection valve includes a housing, a
nozzle body, a valve needle, and a back pressure control part.
[0003] The fuel injection valve includes an inlet connecter. A high pressure pipe having
one end thereof connected to the common rail is connected to the inlet connector.
High pressure fuel is introduced into the inside of the fuel injection valve through
a fuel passage formed in the inside of the inlet connecter. The introduced high pressure
fuel is supplied to a fuel injection hole side formed in the nozzle body and, at the
same time, the introduced high pressure fuel is also supplied to a control chamber
side of the back pressure control part. In the back pressure control part, the fuel
injection is controlled in such a manner that the valve needle is advanced or retracted
by adjusting a pressure in a control chamber thus controlling the opening and the
closing of a fuel injection hole.
[0004] In such a fuel injection valve, when a hard foreign substance is mixed into the fuel,
a valve seat face of a control valve in the back pressure control part corrodes thus
giving rise to a possibility that the fuel injection valve loses accurate fuel injection
control performance. Accordingly, there have been proposed fuel injection valves which
are configured such that a filter is arranged in an inlet connector so as to collect
a foreign substance in high pressure fuel introduced into the fuel injection valve
(see PTL 1 or PTL 2).
[0005] To be more specific, the fuel injection valve described in PTL 1 is configured such
that an edge filter is press-fitted into an inlet connector, and a foreign substance
is collected by using gaps formed by the edge filter as filter meshes.
[0006] The fuel injection valve described in PTL 2 is configured such that a large number
of holes are formed in a portion of a filter body formed into a bag shape which faces
an inner wall surface of an inlet portion. With such a configuration, a foreign substance
in high pressure fuel can be collected by a body portion.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0008] However, the structure of the filter described in PTL 1 has a length in an axial
direction of the inlet connecter thus giving rise to a possibility that a foreign
substance larger than a formed gap passes through the gap. On the other hand, in the
filter described in PTL 2, a reduction in a size of the hole formed in the body portion
is limited and hence, it is difficult for the filter to collect a foreign substance
having a size of several µm which reaches the fuel injection valve.
[0009] Particularly, recently, performance of a fuel main filter mounted on a portion of
an accumulator-type fuel injection control device other than the fuel injection valve
is improved. Accordingly, a foreign substance which reaches the fuel injection valve
is smaller than the gaps of the filter structure of the fuel injection valve and hence,
it has become difficult to collect a foreign substance in fuel using the conventional
filter structure. Further, due to the further increase of a fuel pressure which is
required to cope with recent strict regulation on an exhaust gas, there is a possibility
that the erosion of a valve seat face of the control valve in the back pressure control
part caused by the above-mentioned foreign substance may be accelerated.
[0010] The invention has been made in view of these problems, and it is an object of the
invention to suppress the occurrence of a damage on a valve seat portion of a control
valve of a back pressure control part caused by a foreign substance in high pressure
fuel.
Solution to Problem
[0011] According to the invention, there is provided a fuel injection valve which includes:
a housing having a first fuel passage communicating with a fuel injection hole and
a second fuel passage communicating with a pressure control chamber; a valve needle
movably disposed in the inside of the housing in an advancing and retracting manner;
and a control valve performing an open-close control of the fuel injection hole by
advancing or retracting the valve needle by adjusting a pressure in the pressure control
chamber, wherein the housing includes an inlet opening portion, and an inlet connector
having an introducing passage for high pressure fuel is mounted on the inlet opening
portion, a fuel chamber is formed between an end surface portion of the inlet connector
and a bottom surface portion of the inlet opening portion, the first fuel passage
opens at an outer peripheral portion of the bottom surface portion within a region
of the fuel chamber, and the second fuel passage opens at a center portion of the
bottom surface portion, and the inlet connector is configured such that high pressure
fuel introduced into the fuel chamber from the inlet connector is capable of forming
a swirl flow. Such a fuel injection valve can overcome the above-mentioned drawbacks.
[0012] In the fuel injection valve of the invention, the inlet connector may have: an axial
passage extending in an axial direction; and a circumferential passage extending in
a circumferential direction from the axial passage, disposed offset from the center
of the axial passage, and opens in the fuel chamber.
[0013] In the fuel injection valve of the invention, an end portion of the axial passage
on a fuel chamber side may be closed.
[0014] In the fuel injection valve of the invention, a plurality of the circumferential
passages may be provided.
[0015] In the fuel injection valve of the invention, a diameter of the circumferential passage
may be set equal to or less than a diameter of the fuel injection hole.
[0016] In the fuel injection valve of the invention, a plurality of the circumferential
passages may be provided, and a sum of cross-sectional areas of the circumferential
passages may be set equal to or more than a total cross-sectional area of the fuel
injection hole.
[0017] In the fuel injection valve of the invention, the number of the circumferential passages
may be decided by taking into an account a diameter of the circumferential passage
and the sum of the cross-sectional areas of the circumferential passages.
Advantageous Effect of Invention
[0018] According to the fuel injection valve of the invention, it is possible to suppress
a foreign substance in high pressure fuel which reaches the fuel injection valve from
reaching a back pressure control part side and hence, it is possible to reduce a damage
of a valve seat face of a control valve.
Brief Description of Drawings
[0019]
[Fig. 1] Fig. 1 is a view for explaining the overall constitution of an accumulator-type
fuel injection control device equipped with a fuel injection valve according to this
embodiment.
[Fig. 2] Fig. 2 is a view for explaining an inlet portion of the fuel injection valve
according to this embodiment.
[Fig. 3] Fig. 3 is a view for explaining a swirl flow forming portion of an inlet
connector.
[Fig. 4] Fig. 4 is a view for explaining a bottom surface portion of a fuel chamber.
[Fig. 5] Fig. 5 is a view showing the flow of fuel which flows into the fuel chamber.
Description of Embodiments
[0020] Hereinafter, an embodiment relating to a fuel injection valve of the invention is
specifically explained. However, this embodiment merely describes one mode of the
invention and does not limit the invention. The invention can be altered as desired
within the scope of the invention.
[0021] When the same symbol is used in the respective drawings, the symbol indicates an
identical member unless otherwise specified.
[0022] Fig. 1 is a view schematically showing one example of the overall constitution of
an accumulator-type fuel injection control device equipped with a fuel injection valve
1 according to this embodiment. In Fig. 1, the fuel injection valve 1 is shown in
cross section.
[0023] The accumulator-type fuel injection control device includes, as main constitutional
elements thereof: a supply pump 52 which supplies fuel from a fuel tank 51 under pressure;
a common rail 12 in which high pressure fuel supplied by the supply pump 52 under
pressure is accumulated; and the fuel injection valve 1 which injects high pressure
fuel accumulated in the common rail 12 to the inside of a cylinder of an internal
combustion engine (not shown in the drawing). The overall constitution of this accumulator-type
fuel injection control device per se is substantially equal to the constitution of
a conventionally known accumulator-type fuel injection control device.
[0024] In such an accumulator-type fuel injection control device, the fuel injection valve
1 includes, as main constitutional elements thereof: an injector housing 2; a nozzle
body 3; a valve needle 4; a valve piston 5; a valve body 6; a back pressure control
part 7; and an inlet portion 8. In this embodiment, the injector housing 2 and the
nozzle body 3 correspond to "housing" of the invention.
[0025] The nozzle body 3 is fastened to a distal end portion (a lower end side in Fig. 1)
of the injector housing 2 by a nozzle nut 9. In the injector housing 2 and the nozzle
body 3, first fuel passages 11a, 11b through which high pressure fuel introduced from
the inlet portion 8 is supplied to a fuel reservoir chamber 14 of the nozzle body
3 are formed. Further, in the injector housing 2, a second fuel passage 13 through
which fuel introduced from the inlet portion 8 is supplied to a control chamber 19
of the back pressure control part 7 is formed.
[0026] The fuel reservoir chamber 14 is formed in the nozzle body 3 at a position where
the fuel reservoir chamber 14 faces a pressure receiving portion 4A of the valve needle
4 in an opposed manner. A fuel injection hole 16 is formed in a distal end portion
of the nozzle body 3. The fuel injection hole 16 is closed when a distal end portion
of the valve needle 4 is seated on a seat portion 17 communicating with the fuel injection
hole 16, while the fuel injection hole 16 is opened by separating (lifting) the valve
needle 4 from the seat portion 17. With such a configuration, the injection of fuel
can be started or stopped.
[0027] In the inside of the injector housing 2 to which the nozzle body 3 is fastened, a
spring chamber 22 having a center thereof on a center axis of the injector housing
2 is formed, and a nozzle spring 18 for biasing the valve needle 4 in the direction
toward the seat portion 17 is arranged in the spring chamber 22. Further, the valve
piston 5 is inserted into a hole 2A formed in the injector housing 2, the valve piston
5 is slidably inserted into a slide hole 6A formed in the valve body 6, and is arranged
so as to be positioned in an upper portion of the valve needle 4.
[0028] The control chamber 19 is formed in a portion of the valve body 6 where a top portion
5A of the valve piston 5 is positioned, and the top portion 5A of the valve piston
5 is faced from a lower side (fuel injection hole 16 side). The control chamber 19
communicates with an introducing side orifice 20 formed in the valve body 6. The introducing
side orifice 20 communicates with the second fuel passage 13 through a pressure introducing
chamber 21 formed annularly in a circumferential direction of the valve body 6 between
the valve body 6 and the injector housing 2. With such a configuration, an introduced
pressure from the common rail 12 is supplied to the control chamber 19.
[0029] The control chamber 19 is also communicating with an open-close orifice 23, and the
open-close orifice 23 is openable and closable by operating an electromagnetic valve
28 of the back pressure control part 7 described later. A pressure receiving area
of the top portion 5A of the valve piston 5 in the control chamber 19 is set larger
than a pressure receiving area of the pressure receiving portion 4A of the valve needle
4.
[0030] The back pressure control part 7 includes, as main elements thereof: the electromagnetic
valve 28; a holder 29; and the control chamber 19. The electromagnetic valve 28 includes:
a magnet 25; an armature 27; and a control valve element 24. When a drive signal is
supplied to the magnet 25 from a control circuit, the armature 27 is attracted to
the magnet 25 against a biasing force of the valve spring 26, the control valve element
24 is lifted from a valve seat face continuously formed with the open-close orifice
23 so that a pressure in the control chamber 19 can be released to a fuel return passage
15. In this manner, a pressure in the control chamber 19 is controlled by operating
the control valve element 24 thus controlling a back pressure of the valve needle
4 by way of the valve piston 5 whereby seating of the valve needle 4 on the seat portion
17 and lifting of the valve needle 4 from the seat portion 17 can be controlled.
[0031] In the fuel injection valve 1 having such a configuration, high pressure fuel from
the common rail 12 acts on the pressure receiving portion 4A of the valve needle 4
in the inside of the fuel reservoir chamber 14 from the inlet portion 8 through the
first fuel passages 11a, 11b, and also acts on the top portion 5A of the valve piston
5 in the inside of the control chamber 19 through the second fuel passage 13 and the
pressure introducing chamber 21.
[0032] Accordingly, in a state where the control chamber 19 is cut off from a fuel low pressure
side by the control valve element 24, the valve needle 4 is seated to the seat portion
17 of the nozzle body 3 due to a back pressure of the control chamber 19 which the
valve needle 4 receives by way of the valve piston 5 and a biasing force of the nozzle
spring 18 and hence, the fuel injection hole 16 is closed.
[0033] On the other hand, by supplying the drive signal to the magnet 25 at predetermined
timing, the armature 27 is attracted by the magnet 25 so that the control valve element
24 releases the open-close orifice 23. As a result, a high pressure in the control
chamber 19 returns to the fuel tank 51 through the fuel return passage 15 by way of
the open-close orifice 23. Accordingly, a high pressure acting on the top portion
5A of the valve piston 5 in the control chamber 19 is released so that the valve needle
4 is lifted from the seat portion 17 against a biasing force of the nozzle spring
18 due to a high pressure acting on the pressure receiving portion 4A whereby the
fuel injection hole 16 is released and fuel injection is performed.
[0034] Then, when the magnet 25 is demagnetized so that the open-close orifice 23 is closed
by the control valve element 24, the valve needle 4 is seated to the seat portion
17 at a seating position by way of the valve piston 5 due to a pressure in the control
chamber 19 and a biasing force of the nozzle spring 18 so that the fuel injection
hole 16 is closed and the fuel injection is finished.
[0035] Next, the inlet portion 8 of the fuel injection valve 1 according to this embodiment
is explained in detail.
[0036] Fig. 2 is an enlarged cross-sectional view of the inlet portion 8 of the fuel injection
valve 1 shown in Fig. 1.
[0037] The inlet portion 8 is configured such that an inlet connector 30 is mounted in an
inlet opening portion 2a formed in the injection housing 2. In this embodiment, the
inlet connector 30 is liquid-tightly and threadedly engaged with the inside of the
inlet opening portion 2a.
[0038] The inlet connector 30 includes: a cylindrical connector body 31 having both axial
ends thereof opened; a flow passage forming member 33 held in the inside of the connector
body 31; and a swirl flow forming portion 35 fixed to a distal end of the flow passage
forming member 33. An outer peripheral portion of the flow passage forming member
33 is fixed to the inside of the connector body 31 liquid-tightly by press-fitting,
welding or the like. The swirl flow forming portion 35 is fixed to a distal end surface
of the flow passage forming member 33 by welding or the like.
[0039] An axial passage 33a which opens at both axial ends of the flow passage forming member
33 and constitutes an inflow passage for high pressure fuel is formed in the flow
passage forming member 33. In the swirl flow forming portion 35, an axial passage
35a and a circumferential passage 35b are formed. The axial passage 35a is formed
such that the axial passage 35a opens on one axial side of the swirl flow forming
portion 35, an end portion of the axial passage 35a on a fuel chamber 40 side described
later is closed and the above-mentioned opening communicates with the axial passage
33a of the flow passage forming member 33. The circumferential passage 35b is formed
in an offset manner from the center of the axial passage 35a, and connects the axial
passage 35a and an outer peripheral portion of the swirl flow forming portion 35 to
each other.
[0040] Fig. 3 is a cross sectional view taken along a line A-A in Fig. 2 and viewed from
a direction indicated by an arrow. As shown in Fig. 3, the swirl flow forming portion
35 includes a plurality of circumferential passages 35b formed in an extending manner
in a tangential direction from the axial passage 35a at the center. In the example
shown in Fig. 3, eight circumferential passages 35b extending in the tangential direction
respectively are formed at equal intervals.
[0041] By mounting the inlet connector 30 having such a configuration in the inside of the
inlet opening portion 2a, the fuel chamber 40 is formed by a distal end portion (a
lower side portion shown in Fig. 2) of the inlet connector 30 and a bottom surface
portion 2aa of the inlet opening portion 2a. In this embodiment, a shim member 37
is sandwiched between a front-end-side surface (a lower side surface shown in Fig.
2) of the inlet connector 30 and the bottom surface portion 2aa of the inlet opening
portion 2a so that leakage of high pressure fuel through a gap formed between the
inlet connector 30 and the bottom surface portion 2aa of the inlet opening portion
2a can be suppressed.
[0042] The first fuel passage 11a communicating with the fuel reservoir chamber 14 of the
nozzle body 3 and the second fuel passage 13 communicating with the control chamber
19 of the back pressure control part 7 open at the bottom surface portion 2aa of the
inlet opening portion 2a in a region of the fuel chamber 40.
[0043] Fig. 4 is a view taken along a plane BB (the bottom surface portion 2aa of the inlet
opening portion 2a) in Fig. 2 as viewed from a direction indicated by an arrow. As
shown in Fig. 4, on the bottom surface portion 2aa of the inlet opening portion 2a
in the region of the fuel chamber 40, the first fuel passage 11a opens at an outer
peripheral portion of the bottom surface portion 2aa, and the second fuel passage
13 opens at a center portion of the bottom surface portion 2aa.
[0044] High pressure fuel supplied from the common rail 12 and introduced into the inlet
connector 30 flows through the axial passages 33a, 35a formed in the inside of the
inlet connecter 30 and, thereafter, is introduced into the fuel chamber 40 through
the circumferential passages 35b. At this stage of operation, since the circumferential
passages 35b are formed offset from the center of the axial passage 35a, particularly,
the circumferential passages 35b are formed in the tangential direction in this embodiment,
as shown in Fig. 5, the fuel introduced into the fuel chamber 40 forms a swirl flow.
[0045] Accordingly, a foreign substance mixed into high pressure fuel moves toward the outer
peripheral portion of the fuel chamber 40 due to a centrifugal force and hence, the
foreign substance minimally flows into the second fuel passage 13 communicating with
the control chamber 19 of the back pressure control part 7. That is, in the fuel injection
valve 1 of this embodiment, in place of collecting a foreign substance having a size
of several µm in fuel supplied to the inlet connector 30 from the common rail 12,
the foreign substance is separated to the outer peripheral portion of the fuel chamber
40 and is made to flow into a first fuel passage 11a side whereby fuel having relatively
high cleanliness is made to flow into the control chamber 19 side of the back pressure
control part 7. As a result, the erosion of the valve seat face of the electromagnetic
valve 28 of the back pressure control part 7 by a foreign substance can be reduced.
[0046] In the fuel injection valve 1 of this embodiment, a diameter of the circumferential
passage 35b of the swirl flow forming portion 35 is designed to a value equal to or
less than a diameter of the fuel injection hole 16. For example, the diameter of the
fuel injection hole 16 is approximately 100 µm when the diameter of the fuel injection
hole is small and hence, the diameter of the circumferential passage 35b can be set
to approximately 100 µm. Accordingly, a foreign substance having a size which clogs
the fuel injection hole 16 cannot pass through the circumferential passage 35b in
advance and hence, clogging of the fuel injection hole 16 can be prevented.
[0047] Further, in the fuel injection valve 1 of this embodiment, a sum of cross-sectional
areas of the circumferential passages 35b of the swirl flow forming portion 35 is
designed to be equal to or more than a total cross-sectional area of the fuel injection
hole 16. Accordingly, a pressure loss of high pressure fuel supplied to the fuel injection
valve 1 from the common rail 12 is minimally generated.
[0048] That is, the diameter of the circumferential passage 35b is decided to be equal to
or more than the diameter of the fuel injection hole 16 and, at the same time, the
number of the circumferential passages 35b is decided such that the sum of cross-sectional
areas of the circumferential passages 35b becomes equal to or more than the total
cross-sectional area of the fuel injection hole 16. By forming the circumferential
passages 35b in this manner, a pressure loss of high pressure fuel can be prevented
and, at the same time, clogging of the fuel injection hole 16 by a foreign substance
can be prevented.
1. A fuel injection valve comprising:
a housing having a first fuel passage communicating with a fuel injection hole and
a second fuel passage communicating with a pressure control chamber;
a valve needle movably disposed in the inside of the housing in an advancing and retracting
manner; and
a control valve performing an open-close control of the fuel injection hole by advancing
or retracting the valve needle by adjusting a pressure in the pressure control chamber,
wherein
the housing includes an inlet opening portion, and an inlet connector having an introducing
passage for high pressure fuel is mounted on the inlet opening portion,
a fuel chamber is formed between an end surface portion of the inlet connector and
a bottom surface portion of the inlet opening portion, the first fuel passage opens
at an outer peripheral portion of the bottom surface portion within a region of the
fuel chamber, and the second fuel passage opens at a center portion of the bottom
surface portion, and
the inlet connector is configured such that high pressure fuel introduced into the
fuel chamber from the inlet connector is capable of forming a swirl flow.
2. The fuel injection valve according to claim 1, wherein the inlet connector has: an
axial passage extending in an axial direction; and a circumferential passage extending
in a circumferential direction from the axial passage, disposed offset from the center
of the axial passage, and opens in the fuel chamber.
3. The fuel injection valve according to claim 2, wherein an end portion of the axial
passage on a fuel chamber side is closed.
4. The fuel injection valve according to claim 2 or 3, wherein a plurality of the circumferential
passages are provided.
5. The fuel injection valve according to any one of claims 2 to 4, wherein a diameter
of the circumferential passage is set equal to or less than a diameter of the fuel
injection hole.
6. The fuel injection valve according to any one of claims 2 to 5, wherein a plurality
of the circumferential passages are provided, and a sum of cross-sectional areas of
the circumferential passages is set equal to or more than a total cross-sectional
area of the fuel injection hole.
7. The fuel injection valve according to any one of claims 2 to 6, wherein the number
of the circumferential passages is decided by taking into an account a diameter of
the circumferential passage and the sum of the cross-sectional areas of the circumferential
passages.